U.S. patent number 10,118,015 [Application Number 13/704,619] was granted by the patent office on 2018-11-06 for catheter having flexible tip with multiple flexible segments.
This patent grant is currently assigned to ST. JUDE MEDICAL, ATRIAL FIBRILLATION DIVISION, INC.. The grantee listed for this patent is Alan de la Rama, Cary Hata. Invention is credited to Alan de la Rama, Cary Hata.
United States Patent |
10,118,015 |
de la Rama , et al. |
November 6, 2018 |
Catheter having flexible tip with multiple flexible segments
Abstract
A catheter apparatus includes an elongated body having a distal
portion including a distal end, a plurality of flexible segments,
and at least one intermediate segment that is less flexible than
the flexible segments. Adjacent flexible segments are spaced from
each other longitudinally by the at least one intermediate segment.
Each of the flexible segments include a sidewall having at least
one elongated gap extending at least partially therethrough and
forming interlocking members. The at least one intermediate segment
is shorter than the flexible segments.
Inventors: |
de la Rama; Alan (Cerritos,
CA), Hata; Cary (Irvine, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
de la Rama; Alan
Hata; Cary |
Cerritos
Irvine |
CA
CA |
US
US |
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|
Assignee: |
ST. JUDE MEDICAL, ATRIAL
FIBRILLATION DIVISION, INC. (St. Paul, MN)
|
Family
ID: |
45329305 |
Appl.
No.: |
13/704,619 |
Filed: |
June 16, 2011 |
PCT
Filed: |
June 16, 2011 |
PCT No.: |
PCT/US2011/040781 |
371(c)(1),(2),(4) Date: |
December 16, 2012 |
PCT
Pub. No.: |
WO2011/159955 |
PCT
Pub. Date: |
December 22, 2011 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20130085479 A1 |
Apr 4, 2013 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61355242 |
Jun 16, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M
25/0052 (20130101); A61B 18/1492 (20130101); A61B
2018/00404 (20130101); A61B 2018/1407 (20130101); A61B
2018/00511 (20130101); A61B 2018/00821 (20130101); A61B
2018/00875 (20130101); A61B 2018/00434 (20130101); A61B
2018/00869 (20130101) |
Current International
Class: |
A61M
25/00 (20060101); A61B 18/14 (20060101); A61B
18/00 (20060101) |
Field of
Search: |
;600/33,41,373,424
;604/525 ;606/41 |
References Cited
[Referenced By]
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Other References
"International Search Report and Written Opinion",
PCT/US2011/040781 dated Nov. 25, 2011. cited by applicant .
"International Search Report and Written Opinion",
PCT/US2011/046266 dated Dec. 7, 2011. cited by applicant .
H. Krum et al., "Catheter-based renal sympathetic denervation for
resistant hypertension: a multicentre safety and proof-of-principle
cohort study", www.thelancet.com, Mar. 30, 2009, pp. 1-7. cited by
applicant .
PCT International Search Report (PCT/US2008/069248), dated Jan. 15,
2009, 2 pages. cited by applicant.
|
Primary Examiner: Sirmons; Kevin C
Assistant Examiner: Legette-Thompson; Tiffany
Attorney, Agent or Firm: Armstrong Teasdale LLP
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national stage filing based upon
international application no. PCT/US2011/040781, filed 16 Jun. 2011
and published in English on 22 Dec. 2011 under international
publication no. WO 2011/159955 A1 (the '781 application), which
claims priority to U.S. application No. 61/355,242, filed Jun. 16,
2010 (the '242 application). The '781 application and the '242
application are both hereby incorporated by reference as though
fully set forth herein.
Claims
What is claimed is:
1. A catheter apparatus comprising: an elongated body having a
distal portion including a sidewall, a distal end, a plurality of
flexible segments, and at least one intermediate segment that is
less flexible than said flexible segments, wherein adjacent said
flexible segments are spaced from each other longitudinally by said
at least one intermediate segment, wherein each said flexible
segment comprises a sidewall having at least one elongated gap
extending at least partially therethrough and forming interlocking
members, wherein said at least one intermediate segment is shorter
than said flexible segments, and wherein said each flexible segment
sidewall forms at least a portion of the distal portion sidewall; a
plurality of biasing members that resiliently biases said plurality
of flexible segments to a pre-determined configuration when no
applied force is place on the distal portion, a lumen extension
member having a sidewall and a lumen extending therethrough, said
lumen extension member extending at least partially through said
distal portion and configured such that said lumen extension member
does not compromise a flexibility of the flexible segments, said
lumen extension member coupled to said distal portion; and a
plurality of openings extending through the lumen extension
member.
2. A catheter in accordance with claim 1 wherein said plurality of
flexible segments comprise electrodes and said at least one
intermediate segment comprises a non-conductive member.
3. A catheter in accordance with claim 1 wherein said plurality of
openings includes a first set of openings and a second set of
openings, a size of said openings in said first set of openings
being larger than a size of said openings in said second set of
openings.
4. A catheter in accordance with claim 1 wherein a size of said
openings is configured to provide a substantially constant outflow
of fluid along said distal portion.
5. A catheter in accordance with claim 1, wherein said sidewall is
a substantially cylindrical sidewall provided with elongated gaps
formed at least partially therethrough, the elongated gaps
extending as one or more of an annular gap around a portion of a
circumference of the sidewall, a helical gap forming a helical
pattern on the sidewall, and a gap that outlines alternating
interlocking blocks.
6. A catheter in accordance with claim 1, wherein the at least one
elongated gap extends entirely through said sidewall.
7. A catheter in accordance with claim 1, wherein said distal
portion is bendable about 40 to about 44 degrees relative to a
longitudinal axis of said distal portion.
8. A catheter in accordance with claim 1, wherein said sidewall
comprises alternating interlocking blocks disposed on opposite
sides of the elongated gap, each said block having a head and a
neck, said head being wider than said neck.
9. A distal portion for a catheter, said distal portion comprising:
a distal end; a sidewall; a plurality of flexible segments, each
flexible segment of said plurality of flexible segments comprising
a sidewall that forms at least a portion of the distal portion
sidewall; a plurality of biasing members that resiliently biases
said plurality of flexible segments to a pre-determined
configuration when no applied force is placed on the distal
portion, wherein said plurality of biasing members do not directly
contact said plurality of flexible segments in an at rest position;
and at least one intermediate segment, wherein adjacent said
flexible segments are spaced from each other longitudinally by said
at least one intermediate segment, each said flexible segment
sidewall having at least one elongated gap extending at least
partially therethrough and forming interlocking members, wherein
said at least one intermediate segment is shorter than said
flexible segments, said elongated gaps imparting flexibility to
said flexible segments and enabling different operating
configurations relative to a longitudinal axis.
10. A distal portion in accordance with claim 9, wherein the
different configurations include at least one of a resting length
configuration, a shortened configuration, a substantially straight
configuration, an arcuate configuration, and configurations having
changed cross sectional shapes.
11. A distal portion in accordance with claim 9, wherein said
flexible segments comprise at least one stem and opposing blocks
extending transversely from said stem.
12. A distal portion in accordance with claim 9 wherein said
plurality of flexible segments comprise electrodes and said at
least one intermediate segment comprises a non-conductive
member.
13. A distal portion in accordance with claim 9 further comprising
a lumen extension member having a sidewall and a lumen extending
therethrough, said lumen extension member extending at least
partially through said distal portion.
14. A distal portion in accordance with claim 9, wherein said
flexible segments comprise alternating interlocking blocks disposed
on opposite sides of the elongated gap, each said block having a
head and a neck, said head being wider than said neck.
15. A distal portion in accordance with claim 9 wherein said lumen
extension member includes a plurality of openings extending
therethrough.
16. A distal portion in accordance with claim 15 wherein said
plurality of openings includes a first set of openings and a second
set of openings, a size of said openings in said first set of
openings being larger than a size of said openings in said second
set of openings.
17. A distal portion in accordance with claim 15 wherein a size of
said openings is configured to provide a substantially constant
outflow of fluid along said distal portion.
18. A distal portion for a catheter, said distal portion
comprising: a distal end; a plurality of flexible segments, a
plurality of biasing members that resiliently biases said plurality
of flexible segments to a pre-determined configuration when no
applied force is placed on the distal portion, wherein said
plurality of biasing members do not directly contact said plurality
of flexible segments in an at rest position and; at least one
intermediate segment, wherein adjacent said flexible segments are
spaced from each other longitudinally by said at least one
intermediate segment, each said flexible segment comprising a
sidewall having at least one elongated gap extending at least
partially therethrough and forming interlocking members, wherein
said at least one intermediate segment is shorter than said
flexible segments, said elongated gaps imparting flexibility to
said flexible segments and enabling different operating
configurations relative to a longitudinal axis, wherein said distal
portion is bendable about 40 to about 44 degrees relative to a
longitudinal axis of said distal portion.
Description
BACKGROUND OF THE INVENTION
The field of the invention relates generally to catheters and more
particularly to catheters having flexible tips and including
multiple flexible segments.
Catheters are flexible, tubular devices that are widely used by
physicians performing medical procedures to gain access into
interior regions of the body. Some known catheters include
electrodes that are used for electrically mapping a body part
and/or delivering therapy to an area of the body. These types of
catheters perform best when the electrode has good and sufficient
contact with the tissue that is being treated. It is also
advantageous that the catheter not inadvertently damage tissue
while it is inside the body.
BRIEF DESCRIPTION OF THE INVENTION
In one aspect, a catheter apparatus includes an elongated body
having a distal portion including a distal end, a plurality of
flexible segments, and at least one intermediate segment that is
less flexible than the flexible segments. Adjacent flexible
segments are spaced from each other longitudinally by the at least
one intermediate segment. Each of the flexible segments includes a
sidewall having at least one elongated gap extending at least
partially therethrough and forming interlocking members. The at
least one intermediate segment is shorter than the flexible
segments.
In another aspect, a distal portion for a catheter includes a
distal end, a plurality of flexible segments, and at least one
intermediate segment. Adjacent flexible segments are spaced from
each other longitudinally by the at least one intermediate segment.
Each flexible segment includes a sidewall having at least one
elongated gap extending at least partially therethrough and forming
interlocking members. The at least one intermediate segment is
shorter than the flexible segments. The elongated gaps impart
flexibility to the flexible segments and enable different operating
configurations relative to a longitudinal axis.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of a distal portion of an ablation
catheter according to one embodiment of the invention.
FIG. 2 is an expanded view of an interlocking pattern formed by
channels in the catheter shown in FIG. 1.
FIG. 3 illustrates a stem member including interlocking members
formed by the channels shown in FIG. 2.
FIG. 4 illustrates an alternative interlocking pattern having
rounded members.
FIG. 5 is a partial cross-sectional view of the distal portion of
the ablation catheter shown in FIG. 1.
FIG. 6 is a schematic view of a distal portion of an ablation
catheter according to a second embodiment of the invention.
FIG. 7 is a partial cross-sectional view of the distal portion of
the ablation catheter shown in FIG. 6.
FIG. 8 is a partial cross-sectional view of another embodiment of a
distal portion of an ablation catheter similar to the catheter
shown in FIG. 6 that has an alternative opening pattern.
DETAILED DESCRIPTION OF THE INVENTION
The invention can now be better understood by turning to the
following detailed description of numerous embodiments, which are
presented as illustrated examples of the invention defined in the
claims. It is expressly understood that the invention as defined by
the claims may be broader than the illustrated embodiments
described below.
Embodiments of ablation catheters having tips including flexible
and bendable electrodes, and also freedom of movement to shorten an
axial length of the catheter tip, while reliably creating linear
lesions in body tissues are described. The flexibility of the
electrodes increases an electrode-to-tissue contact area, and in
turn improves ablation of tissue. Especially in tissue where ridges
are present, the flexible tip electrodes can be dragged across the
ridges with improved continuous electrode-to-tissue contact.
These and other benefits are accomplished by providing a flexible
distal portion for a catheter that includes a plurality of flexible
segments that each include a generally hollow cylindrical structure
having an interior lumen. A rounded distal end may be provided. The
cylindrical wall of the flexible segment may have a variety of
different types of channels or elongated grooves defining gaps in
the cylindrical wall and imparting some flexibility thereto,
including flexing and bending capability. In some embodiments, the
catheter is an ablation catheter and the flexible segments are
electrodes. This flexibility allows the flexible electrodes to
conform to and establish sufficient surface contact with body
tissues that may have irregular surface area including ridges and
the like, and tissues that may be contracting and stretching, or
moving, to more reliably create linear lesions on the body tissue.
The electrodes also are configured to provide a freedom of movement
and shortening of a length of the catheter tip along its
longitudinal axis to maintain surface contact with, for example,
contracting and stretching, or moving tissue that is targeted for
ablation. The channels, grooves, and associated elongated gaps may
have various shapes, sizes and overall configurations as explained
below in numerous exemplary embodiments.
FIG. 1 is a schematic view of a distal portion 10 of an ablation
catheter according to one embodiment of the invention. Distal
portion 10 includes a flat distal end 12 that is substantially
circular and has a rounded edge at its perimeter. In an alternative
embodiment, distal end 12 is domed shaped and has a curved distal
end. In another embodiment, distal end 12 is oval or elliptical
shaped. Distal portion 10 also includes a distal flexible segment
14 and a proximal flexible segment 16. Flexible segments 14, 16 are
separated by an intermediate segment 18. In one embodiment,
flexible segments 14, 16 are electrodes and intermediate segment 18
is a nonconductive member, and intermediate segment 18 is less
flexible than flexible segments 14, 16. In an alternative
embodiment, intermediate segment 18 is as flexible as flexible
segments 14, 16. Distal flexible segment 14 is coupled to distal
end 12 and to intermediate segment 18. Proximal flexible segment 16
is coupled to intermediate segment 18 and a catheter shaft 20.
Non-conductive intermediate segment 18 electrically isolates
flexible electrode segments 14, 16 and secures flexible electrode
segments 14, 16 thereto. As seen in FIG. 1, intermediate segment 18
has T-shaped protrusions 19 that match and fit within corresponding
T-shaped voids or cavities on the edges of flexible electrode
segments 14, 16 to form interlocking connections that couple
flexible electrode segments 14, 16 to intermediate segment 18. Of
course, other configurations can be used to form the connections as
long as electrode segments 14, 16 are secured to intermediate
section 18. In one embodiment non-conductive intermediate segment
18 is made of polyimide or some other nonconductive material. It
may be formed as a strip and then bent into a tubular shape to form
the interconnecting coupling between flexible electrode segments
14, 16. The length of intermediate segment 18 is sufficiently small
to allow the ablation zones of flexible electrode segments 14, 16
to overlap and form a continuous lesion. The short length of
intermediate segment 18 also preserves the overall flexibility of
distal portion 10 by limiting the size of intermediate segment 18,
which is non-flexible or at least not as flexible as electrode
segments 14, 16. In one example, flexible electrode segments 14, 16
are each about 4 mm in length while intermediate segment 18 is
about 1 mm in length. Typically, intermediate segment 18 is
substantially shorter in length than flexible electrode segments
14, 16 (e.g., preferably less than a half, more preferably less
than a third, and most preferably less than a fourth).
Distal flexible electrode segment 14 includes a cylindrical
sidewall 22 and proximal flexible electrode segment 16 includes a
cylindrical sidewall 24. Sidewalls 22, 24 have helical or spiral
channels or grooves 26 cut or otherwise formed entirely through
sidewalls 22, 24 to create elongated gaps or openings. As used
herein, an elongated opening preferably has a length that is at
least about 3 times the width of the opening, more preferably at
least about 5 times, and most preferably at least about 10
times.
In an alternative embodiment, sidewalls 22, 24 include helical or
spiral channels or grooves forming elongated gaps or openings that
do not extend entirely through sidewalls 22, 24. Channels or
grooves 26 that do not extend entirely through sidewalls 22, 24,
define elongated openings of decreased wall thickness and decreased
cross-sectional area of sidewalls 22, 24 and hence the areas of the
wall that include channels 26 are structurally weaker and less
rigid than areas of sidewalls 22, 24 where the elongated openings
are not present, imparting flexible properties to the electrode
wall. As used herein, an elongated opening preferably has a length
that is at least about 3 times the width of the groove, more
preferably at least about 5 times, and most preferably at least
about 10 times. As can be appreciated, channels 26 extending
completely through electrode sidewalls 22, 24 will generally impart
more flexibility, or less rigidity, to sidewalls 22, 24 than will
channels 26 that do not extend entirely through sidewalls 22,
24.
In a further alternative embodiment, the channels extend in a
circular and planar configuration, with each channel being
equidistant from adjacent channels. In additional embodiments, the
channels have a non-planar helical configuration that completes
more or less than one 360 degree loop or turn on the surface of the
electrode sidewall. Each of these channels has discrete end points
and each electrode includes multiple channels.
In another embodiment, the electrode may include annular rings
extending in a plane that do not form a continuous unending loop,
but rather channels forming loops having two terminal ends that are
spaced apart from one another. A further embodiment may include a
combination of continuous and non-continuous, planar and non-planar
channel configurations.
As shown in FIG. 1, channels 26 each form interlocking members and
create an interlocking pattern that follows a continuous helical
path configuration from one end of flexible segment 14 to the other
and from one end of flexible segment 16 to the other. Channels 26
outline alternating interlocking members, or blocks 28.
Blocks 28 are disposed on both sides of channel 26. Each block 28
has a head 30 and a neck 32, wherein head 30 is wider than neck 32.
As shown in FIG. 2, an interlocking pattern includes a first head,
represented by "Y", which has a neck 32 situated on one side of
channel 26, disposed between second and third heads, represented by
"X". Second and third heads X each have necks situated on the other
side of channel 26 and on opposite sides of head Y. Adjacent blocks
28 are interlocked because head 30 is wider than adjacent necks 32
and is therefore locked between adjacent necks 32. For example,
second and third heads X in FIG. 2 are separated by a shortest
distance A in FIG. 2, and distance A is shorter than a width W of
the head Y, thereby restricting relative movement of two adjacent
loops away from each other and preventing adjacent blocks 28 from
separating.
Contemplated patterns of elongated openings can also be described
according to structures of sidewalls 22, 24, instead of the shape
of channel 26. For example, FIG. 3 illustrates an electrode wall
including a stem member 34 that helically extends about a
longitudinal axis of the electrode forming a series of stem loops
(see FIG. 1). Stem member 34 includes a plurality of protruding
blocks 28 peripherally disposed on both sides of stem member 34.
Each block 28 transversely extends in a lateral direction indicated
by arrow T in FIG. 3 toward an adjacent stem loop in electrode
sidewall 22 shown in FIG. 1. Each adjacent stem member 34 includes
blocks 28 that are staggered from blocks 28 in immediately adjacent
stem members, resulting in an interlocking block pattern. Blocks 28
extending from stem member 34 can have various shapes. For example,
at least some blocks 28 may have a shape of an upside down triangle
as illustrated, where one angle of the triangle represents the neck
region.
FIG. 4 illustrates an alternative embodiment having alternatively
shaped blocks 36 having a rounded bulbous shape. Contemplated heads
of the bulbous protrusions are wider than their corresponding
necks, facilitating an interlocking block pattern.
Referring back to FIGS. 1 and 3, stem members 34 have an axis 38
that extends in a helix about a longitudinal axis F with a pitch
between and including 0.5 to 10 degrees. Channels 26 between blocks
28 of stem members 34 improve a flexibility of flexible segments,
or electrodes, 14, 16, and allow electrodes 14, 16 to flex and bend
along their longitudinal length and relative to the catheter body
to which they are attached. For example, the ability of electrodes
14, 16 to flex allows an approximately 4 mm length of a respective
electrode 14, 16 to bend between and including 0.2 degrees to 70
degrees relative to the longitudinal axis from a substantially
straight position. More specifically, the ability to flex allows an
approximately 4 mm electrode length to bend between and including 5
degrees to 50 degrees relative to the longitudinal axis from a
substantially straight position. Even more specifically, the
ability to flex allows an approximately 4 mm electrode length to
bend about 20 to 22 degrees relative to the longitudinal axis from
a substantially straight position and, accordingly, distal portion
10 which has two 4 mm electrodes 14, 16 will bend approximately 40
to 44 degrees.
The ability of electrodes 14, 16 to flex provides better contact
with the target tissue, for example, in the trabeculated
endocardial tissue where there are valleys, ridges, and pockets in
the tissue surface. Electrode-to-tissue contact area is increased
by using sidewalls 22, 24 of electrodes 14, 16, respectively, to
deliver energy for ablation. The increased contact surface
increases the likelihood of creating larger lesions at a given
contact force and power setting. This in turn enables deeper
ablation without having to increase the power setting, which is
beneficial because increased power settings may undesirably
increase the likelihood of coagulation.
Flexible electrodes 14, 16 are configured to absorb contraction and
stretching of tissue, and improve continuous tissue contact in a
beating heart during systole and diastole, whether electrodes 14,
16 contact the tissue in a parallel, perpendicular, or other
orientation. Continuous tissue contact is also maintained
regardless of whether the electrode is stationary at one location
or when the electrode is in motion and being dragged. Without such
flexibility, a standard rigid tip electrode would "jump off" of the
tissue in response to a beating heart.
Alternative embodiments of flexible electrodes for catheters
include physiologic-sensing capability to measure different aspects
of the body. Such capability is obtained by using one or more
sensors located at distal portion 10 of the catheter. Such a sensor
may be disposed within the hollow electrode to measure one or more
physiologic aspects related to a procedure. Such data can be
collected and monitored by the operator during the procedure.
Unlike known elongated electrodes (e.g., U.S. Pat. No. 6,063,080),
which can be laid across a tissue to create relatively long linear
lesions, the flexible electrodes as described have the unexpected
advantage of improving precision in mapping and control at specific
locations within the heart for more precise ablation, especially in
relatively tight anatomical structures. Known elongated electrodes
have difficulty positioning in such tight anatomical
structures.
One unexpected advantage achieved with a flexible tip electrode is
minimized "flipping." When a standard rigid tip electrode is
manipulated within a body cavity having valleys and pockets in the
tissue, the tip electrode can get caught or stuck in the tissue. As
a physician continues to apply force in an attempt to move the tip
electrode even though it is caught or stuck, the tip electrode may
suddenly "flip" out of the tissue. Such "flipping" is highly
undesirable and should be avoided. The proposed flexible tip
electrodes greatly minimize "flipping" issues, and allow smoother
dragging and motion across valleys and pockets in target tissue. In
addition, one or more pulling wires (not shown) can be utilized
with distal portion 10. In one embodiment, pulling wires are
anchored to distal end 12 and extend through a proximal end of the
catheter such that an operator can manipulate distal portion 10 of
the catheter. In an alternative embodiment, a distal end of the
pulling wire is connected to the catheter at a location other than
distal end 12. The pulling wires allow the operator to configure
distal portion 10 in different directions and curvatures during
insertion of the catheter as well as during the procedure. In one
embodiment, the pulling wires are anchored as traditionally known
in the art and may extend through the catheter wall or may extend
through a lumen. Multiple wires may be anchored at set lengths from
distal end 12 in pairs on opposite sides of the catheter, or the
anchor points may be offset and thus allow for asymmetric
curvatures and sweep.
FIG. 5 is a partial cross-sectional view of distal portion 10 of
the ablation catheter of FIG. 1. A tube 40 is disposed internally
between flexible electrode segments 14, 16, and is attached to
flexible electrode segments 14, 16 by an adhesive 42 or the like.
In one embodiment, tube 40 is fabricated from a PEEK tube. In an
alternative embodiment tube 40 is fabricated from other suitable
nonconductive materials. A distal spring coil 44 extends between
distal end 12 and tube 40. A proximal spring coil 46 extends
between tube 40 and a tip stem 48 and is attached to proximal
electrode segment 16 and catheter shaft 20. Spring coils 44, 46
bias flexible electrode segments 14, 16 to stretch lengthwise.
Spring coils 44, 46 provide resilient biasing supports for flexible
electrode segments 14, 16, respectively, both when sidewalls 22, 24
have channels 26 extending completely therethrough and when
sidewalls 22, 24 have channels that do not extend completely
therethrough. Spring coils 44, 46 provide structural integrity to
sidewalls 22, 24, respectively, and resiliently maintain flexible
electrode segments 14, 16 in a pre-determined configuration when no
applied force is placed on distal portion 10. In an alternative
embodiment, biasing members other than spring coils can be used to
bias electrode segments 14, 16 to stretch lengthwise. As shown in
FIG. 5, the pre-determined electrode configuration at rest orients
the longitudinal axis of each flexible electrode segment 14, 16
along a straight line. In a different embodiment, the
pre-determined configuration at rest may orient the longitudinal
axes of electrode segments 14, 16 along a curved or arcuate path.
Such a configuration may be imparted to distal portion 10 through
use of suitable shape memory alloys.
Channels 26 that extend entirely through electrode sidewalls 22, 24
provide a sufficient gap in sidewalls 22, 24 to allow shortening of
a length of electrode segments 14, 16 when a sufficient force is
applied to the electrode. As explained above, channel 26 extends,
for example, between a head 30 and a neck 32 of an adjacent loop in
electrode sidewalls 22, 24, and allows a freedom of movement
between adjacent stems along the longitudinal axis of the electrode
wall when channel 26 is narrowed or closed. Likewise, channel 26
between adjacent heads 30 provides a freedom of movement for
lengthening of electrode sidewalls 22, 24 along the longitudinal
length of electrode flexible segments 14, 16 when channel 26 is
opened or widened. Such shortening or lengthening may involve
widening or narrowing one or more channels 26 in the various
embodiments described above.
In an exemplary embodiment, flexible electrode segments 14, 16 can
shorten between and including 0.2% to 10% of an axial resting
length of flexible electrode segments 14, 16 when channels 26 in
electrode sidewalls 22, 24 are closed. In one embodiment, channels
26 in electrode sidewalls 22, 24 allow shortening of the axial
length between and including 0.1% to 8% of the resting length. More
specifically, channels 26 in electrode sidewalls 22, 24 allow axial
shortening of the length between and including 0.5% to 5% of the
resting length, and even more specifically, channels 26 in
electrode sidewalls 22, 24 allow shortening of the resting length
between and including 0.1% to 0.5% of the length.
In one embodiment, an at rest electrode segment 14, 16, assumes a
pre-determined shape stretching in the longitudinal direction and
opening channels 26 a predetermined amount. When electrode segments
14, 16 contact tissue, an applied compressive force causes channels
26 to narrow or close and electrode segments 14, 16 shorten against
the force. Once shortened, the width of channels 26 is decreased
and may fully close such that the length of electrode segments 14,
16 reach a minimum axial length that is substantially unaffected by
further exertion of applied force.
In the exemplary embodiment, spring coils 44, 46, or flexible
electrodes 14, 16, or any combination thereof, may be, and in one
embodiment is, fabricated from biocompatible materials that are
suitable for ablation temperatures. Such materials include, without
limitation, natural and synthetic polymers, various metals and
metal alloys, Nitinol, naturally occurring materials, textile
fibers, and combinations thereof. In the exemplary embodiment,
distal portion 10, and other catheter components including, without
limitation, flexible segments 14, 16 and coils 44, 46, are
fabricated from a substantially or entirely non-magnetic,
non-electrically conductive, and non-RF reactive material to enable
magnetic resonance imaging (MRI) of distal portion 10 using an MRI
system (not shown) for positioning and/or orienting distal portion
10. While the above described catheter is advantageous for use with
an MRI system, it is contemplated that magnetic fields and
gradients to generate images of distal portion 10 may alternatively
be generated by other systems and techniques if desired. For
example, in one embodiment, all, or a portion of, distal portion 10
is fabricated from 90% platinum and 10% iridium, or other materials
known in the art, such that all or part of distal portion 10 is
viewable under fluoroscopic exposure.
Additionally or alternatively, distal portion 10 may include and/or
be coated with a conductive material including, without limitation,
gold and/or platinum, to increase a thermal conductivity of the
electrodes. Moreover, distal portion 10 can be and, in one
embodiment, is coated with heparin to provide an anticoagulation
effect. Furthermore, distal portion 10 can be and, in one
embodiment, is electro-polished to reduce sharp edges.
In a further alternative embodiment, the catheter can be used with
an electric field-based system, such as, for example, the EnSite
NavX.TM. system commercially available from St. Jude Medical, Inc.,
and as generally shown with reference to U.S. Pat. No. 7,263,397
entitled "Method and Apparatus for Catheter Navigation and Location
and Mapping in the Heart," the disclosure of which is incorporated
herein by reference in its entirety. In other embodiments, the
catheter can be used with systems other than electric field-based
systems. For example, a magnetic field-based system such as the
Carto.TM. system commercially available from Biosense Webster, and
as generally shown with reference to one or more of U.S. Pat. No.
6,498,944 entitled "Intrabody Measurement;" U.S. Pat. No. 6,788,967
entitled "Medical Diagnosis, Treatment and Imaging Systems;" and
U.S. Pat. No. 6,690,963 entitled "System and Method for Determining
the Location and Orientation of an Invasive Medical Instrument,"
the disclosures of which are incorporated herein by reference in
their entireties. In other embodiments, the catheter can be used
with a magnetic field-based system such as the gMPS system
commercially available from MediGuide Ltd., and as generally shown
with reference to one or more of U.S. Pat. No. 6,233,476 entitled
"Medical Positioning System;" U.S. Pat. No. 7,197,354 entitled
"System for Determining the Position and Orientation of a
Catheter;" and U.S. Pat. No. 7,386,339 entitled "Medical Imaging
and Navigation System," the disclosures of which are incorporated
herein by reference in their entireties. In yet another embodiment,
the catheter can be used with a combination electric field-based
and magnetic field-based system, such as, for example and without
limitation, the Carto 3.TM. system also commercially available from
Biosense Webster, and as generally shown with reference to U.S.
Pat. No. 7,536,218 entitled "Hybrid Magnetic-Based and Impedance
Based Position Sensing," the disclosure of which is incorporated
herein by reference in its entirety. In yet still other exemplary
embodiments, the catheter can be used in conjunction with other
commonly available systems, such as, for example and without
limitation, fluoroscopic, computed tomography (CT), and magnetic
resonance imaging (MRI)-based systems. In these embodiments, the
catheter includes one or more tracking elements that enable the
location of the catheter to be tracked. Such tracking elements can
include active and/or passive elements such as sensors and/or
electrodes.
As seen in FIGS. 1 and 5, a pair of band electrodes 50 is provided
on catheter shaft 20 and may be used for diagnostic purposes or the
like. A pair of electrode wires 51 extends to band electrodes 50
and provides energy to band electrodes 50. Distal portion 10 also
includes conductor wires 52, 53 and thermocouples 54, 55. An
adhesive 56, such as urethane, maintains conductor wire 52 and
thermocouple 54 in place at distal end 12. In one embodiment,
distal end 12 is in electrical and thermal contact with distal
flexible electrode segment 14. Conductor wire 53 and thermocouple
55 are coupled to tip stem 48 and held in place with an adhesive,
such as urethane. In one embodiment, tip stem 48 is in electrical
and thermal contact with proximal flexible electrode segment 16.
Conductor wires and thermocouples may also be provided at other
locations at or near other electrodes or electrode segments. Wires
51, 52, 53 are coupled at their proximal end to an energy source as
is well known in the art. In addition, thermocouples 54, 55 are
coupled to an energy source at their proximal end as is well known
in the art. Accordingly, flexible electrodes 14, 16 can be
energized sequentially or simultaneously. In one embodiment, distal
portion 10 can be operated in a temperature control mode and/or in
a power control mode. In an alternative embodiment, distal end 12
is unitary with flexible electrode segment 14 and tip stem 48 is
unitary with proximal flexible electrode segment 16.
Catheters having flexible tip electrodes such as those described
above can optionally be coupled to an irrigation system. That is,
the catheter may include a fluid delivery lumen in the tubular
catheter body, with the fluid delivery lumen in fluid communication
with electrode segments 14, 16 and distal end 12. When one or more
of the flexible electrodes change shape under an applied force, the
elongated gap(s) will undergo changes in size and/or shape, thereby
affecting the fluid flow therethrough. A cooling fluid, for
example, may be pumped in an open flow path through the catheter
body to the hollow lumen of the electrode, where it may pass
through the gap(s) in the electrode sidewall to the exterior of the
electrode, bathing the electrode and adjacent body tissue with
cooling fluid. Alternatively, an internal, closed-loop irrigation
system using re-circulated cooling fluid as known in the art is
also possible. Also, catheters having flexible electrodes can be
coupled to an energy source, such as a radio frequency (RF)
generator to provide energy needed for tissue ablation. RF signal
generators are known and are disclosed, for example, in U.S. Pat.
No. 6,235,022.
In one embodiment, and as shown in FIG. 5, distal portion 10
includes a lumen tubing 60 leading distally to a lumen extension
member 62 which extends through proximal flexible segment 16 and
partially through distal flexible segment 14. Alternatively, lumen
extension member 62 extends through proximal flexible segment 16,
completely through distal flexible segment 14 and is in fluid
communication with exit ports 63 that extend through distal end 12.
In a further embodiment, lumen extension member 62 may have any
suitable length that does not compromise a flexibility of distal
potion 10, such as, for example, a length that is up to
approximately 90 percent of a length of distal portion 10. Lumen
extension member 62 defines an extended fluid lumen extending
through flexible segments 14 and 16, and enables fluid to be
channeled from lumen tubing 60 along a longitudinal length of
distal portion 10. As such, lumen extension member 62 is in fluid
communication with lumen tubing 60. Lumen extension member 62 is
configured to provide a substantially constant outflow of fluid
along the longitudinal length thereof. Such configurations include
openings 64 of sizes and arrangements that may vary from a proximal
end 66 to a distal end 68 of lumen extension member 62 to provide a
desired (e.g., substantially uniform) irrigation pattern or fluid
flow through distal portion 10 and channels 26, as well as lumen
shapes and sizes to provide for a substantially constant outflow of
fluid.
Lumen extension member 62 can be, and in one embodiment is,
fabricated from a suitable biocompatible material including at
least one of a polyimide material, a polyether block amide
material, a silicone material, and a polyurethane material. In the
exemplary embodiment, lumen extension member 62 is fabricated from
a material that is substantially similar to the material used to
fabricate catheter shaft 20. Alternatively, lumen extension member
62 can be and, in one embodiment, is fabricated from a
biocompatible material that is different from the biocompatible
material used to fabricate catheter shaft 20. In the exemplary
embodiment, lumen extension member 62 is fabricated from a
polyimide material.
Lumen extension member 62 may have any suitable cross-sectional
shape to enable channeling fluid therethrough. In the exemplary
embodiment, lumen extension member 62 has a substantially rounded
cross-sectional shape such as one of a circle, an ellipse, and an
oval. Moreover, lumen extension member 62 may have any suitable
number of portions each having any suitable geometry extending
along a longitudinal length of lumen extension member 62. For
example, lumen extension member 62 may have a substantially uniform
geometry extending along the longitudinal length of lumen extension
member 62. Moreover, lumen extension member 62 may have a
funnel-shaped geometry extending along the longitudinal length of
lumen extension member 62. For example, a funnel-shaped
lumen-extension member has a diameter that gradually increases
along the longitudinal length of lumen extension member 62 from
proximal end 66 to distal end 68. In the exemplary embodiment,
lumen extension member 62 includes a proximal portion having a
first geometry and a distal portion having a second geometry. Lumen
extension member 62 can be formed of, or is partially or entirely
coated or lined with, a thermally conductive material to insulate
the irrigation fluid, chemicals, therapeutic substances, gels,
cooling or heating solutions, and the like from the body or
electrode energy.
In one embodiment, a flow constrictor (not shown) is utilized to
manipulate the fluid outflow through openings 64. In this
embodiment, the flow constrictor decreases a lumen diameter along a
longitudinal length of lumen extension member 62 between successive
sets of openings 64. Such a flow constrictor can be configured to
provide a substantially constant fluid flow through openings 64
along a longitudinal length of lumen extension member 62, when
utilized with appropriately sized and shaped openings.
In the exemplary embodiment, openings 64 extend through a sidewall
of lumen extension member 62 to enable channeling fluid flow along
the longitudinal length of distal portion 10. Each opening 64 may
have any suitable configuration. In the exemplary embodiment, each
opening 64 has a substantially rounded shape such as a circle, an
ellipse, and an oval. Moreover, in the exemplary embodiment, at
least one opening 64 has an axis that is substantially
perpendicular to the longitudinal length of lumen extension member
62. Furthermore, in the exemplary embodiment, at least one opening
64 has a diameter of approximately 0.05 mm to approximately 0.20
mm. In one embodiment, lumen extension member 62 is fabricated from
a material that enables openings 64 to change size and or
configuration when member 62 is flexed. Such changes include
openings 64 becoming larger or smaller as member 62 flexes and/or
openings 64 changing shape from circular to oval or elliptical, or
changing shape from oval or elliptical to circular. This embodiment
would enable more fluid to flow towards tissue being ablated due to
the curvature of distal portion 10 as tissue is contacted.
In one embodiment, openings 64 include a first set of openings 65
and a second set of openings 67. Openings in first set 65 are
larger than openings in second set 67. In one embodiment, second
set openings 67 are about half the size of first set openings 65.
These differently sized openings 64 allow for a substantially
constant fluid flow through openings 64. As shown in FIG. 5, first
set of openings 65 are proximal to second set of openings 67 within
each flexible electrode 14, 16. FIG. 8 illustrates another
configuration of openings 64 in which second set of openings 67 is
proximal to the first set of openings 65 within flexible electrode
16 and first set of openings 65 is proximal second set of openings
67 within flexible electrode 14. Alternatively, any pattern of
openings could be utilized that provides a substantially constant
fluid flow such as first set of openings 65 proximal to second set
of openings 67 within flexible electrode 16 and second set of
openings 67 proximal to first set of openings 65 within flexible
electrode 14, as well as second set of openings 67 proximal to
first set of openings 65 within each flexible electrode 14, 16.
First set of openings 65 and second set of openings 67 each may
include any suitable quantity of openings. For example, first set
of openings 65 may include a first quantity of openings, and second
set of openings 67 may include a second quantity of openings. In
the exemplary embodiment, the first quantity is equal to the second
quantity. Alternatively, the first quantity can be and, in one
embodiment, is more or less than the second quantity.
In an alternative embodiment, a dedicated lumen extension member
(not shown) extends to each flexible segment and to distal end 12
such that a uniform amount and rate of fluid is delivered to each
flexible segment 14, 16 and to distal end 12 to provide uniform
fluid outflow through channels 26 in each flexible segment 14, 16
and through exit ports 63. Such dedicated lumen extension members
can extend through an entire length of catheter 20 or they may each
connect to, and extend from, lumen tubing 60. In a further
alternative embodiment, no lumen extension member is utilized and
lumen tubing 60 ends proximally of proximal flexible segment 16 to
allow for increased flexibility of flexible segments 14, 16 and
hence distal portion 10. In one embodiment, distal end 68 of lumen
extension member 62 is plugged to prevent fluid outflow therefrom.
Alternatively, one or more openings can extend through plugged
distal end 68 to allow fluid to flow therethrough.
Embodiments of ablation catheters including a distal portion 10 and
a lumen extension member 62 facilitate providing a radially
directed irrigation pattern that is substantially uniform along a
longitudinal length of distal portion 10 when distal portion 10 is
in the unflexed, or relaxed state. In addition, lumen extension
member 62 provides a varying fluid flow along the longitudinal
length of distal portion 10 due to the variations in size of the
openings or gaps formed by channels 26 when flexible electrodes 14,
16 are in the flexed position. For example, more fluid flows toward
the tissue surface than away from the tissue surface during a
procedure due to the gaps becoming more open toward the tissue
surface and less open away from the tissue surface.
As seen in FIG. 5, fluid that exits within proximal flexible
electrode 16 can flow through tube 40 and exit distal portion 10
through channels 26 that extend through distal flexible electrode
14. As well, fluid that exits within distal flexible electrode 14
can flow through tube 40 and exit distal portion 10 through
channels 26 that extend through proximal flexible electrode 16.
Alternatively, tube 40 can be plugged so fluid cannot flow
therethrough between proximal flexible electrode 16 and distal
flexible electrode 14.
Flexible tip electrodes for ablation catheters may be formed and
fabricated, for example, according to the following methodology. An
exemplary method includes providing a hollow cylindrical electrode,
and applying a laser to the cylindrical wall of the electrode to
cut through a wall of the electrode. The laser cuts the wall in a
pre-determined pattern that may extend helically around the
circumference of the electrode wall, or may conform to any of the
elongated groove or opening patterns previously described above in
the various embodiments. The cuts create channels 26 that are
consistently wider in some sections and narrower in other sections.
The wider sections allow freedom of movement to narrow or widen
channels 26 as previously described, making it possible to shorten
an axial length of at least one of flexible electrodes 14, 16 when
a force is applied proximally at distal portion 10.
FIG. 6 is a schematic view of a distal portion 70 of an ablation
catheter according to a second embodiment of the present invention.
FIG. 7 is a partial cross-sectional view of distal portion 70 of
the ablation catheter shown in FIG. 6. FIGS. 6 and 7 differ from
FIGS. 1 and 2 in the configurations of intermediate segment 72 and
tube 74 and the connection they provide to flexible electrode
segments 14, 16. As shown in FIGS. 6 and 7, tube 74 has external
threads that engage internal threads of intermediate segment 72 and
flexible electrode segments 14, 16, so as to provide a threaded
connection. In addition, a band electrode 76 is included on an
external surface of intermediate segment 70 and an electrode wire
77 extends to band electrode 76 and provides energy to band
electrodes 76. Wire 77 is coupled at its proximal end to an energy
source as is well known in the art.
FIGS. 1-8 illustrate a distal portion of an ablation catheter that
includes two flexible electrode segments. In other embodiments,
there may be three or more flexible electrode segments. Each pair
of neighboring flexible electrode segments are separated by an
electrically nonconductive segment.
Recent angiographic studies have shown a highly variable
cavotricuspid isthmus anatomy with various configurations and
topography, which may lead to difficulties in some atrial flutter
cases. Placing a long-tipped, rigid 8 mm electrode into pouch-like
recesses found in these patients may present technical challenges.
The multi-segmented flexible tip catheter design may better enable
the electrodes to synchronously maintain tissue contact with the
beating heart and also facilitate the creation of a linear lesion.
This tip may also be advantageous in ablating within the
trabeculated endocardial regions of patients with ventricular
tachyarrhythmias, and in ablating the roof lines in atrial
fibrillation procedures. It may also be useful when ablating within
the coronary sinus.
The many embodiments of flexible electrodes facilitate performing
linear ablation procedures. As with typical ablation catheters, a
physician can perform mapping using the electrodes, and determine a
target site for ablation. Once determined, the physician drags the
flexible tip electrode across the target tissue to start ablation
while applying energy to the tissue. Because the electrode is
flexible, the electrode can be more easily dragged across tissue
surfaces having ridges and bumps while keeping constant
electrode-to-tissue contact. This is possible because the flexible
tip electrode deforms and/or flexes when it is dragged across a
tissue surface. The flexible and deformable properties of the
flexible tips results in greater electrode-to-tissue surface area
than would otherwise be possible with a rigid tip electrode. And
because the gaps in the electrode wall allows the electrode to be
shortened when pressed tip-down against tissue surface, accidental
tissue-perforation is largely avoided if not eliminated.
This written description uses examples to disclose the invention,
including the best mode, and also to enable any person skilled in
the art to practice the invention, including making and using any
devices or systems and performing any incorporated methods. Many
alterations and modifications may be made by those having ordinary
skill in the art without departing from the spirit and scope of the
invention. Therefore, it must be understood that the illustrated
embodiments have been set forth only for the purposes of example
and that it should not be taken as limiting the invention as
defined by the following claims.
The patentable scope of the invention is defined by the claims, and
may include other examples that occur to those skilled in the art.
Such other examples are intended to be within the scope of the
claims if they have structural elements that do not differ from the
literal language of the claims, or if they include equivalent
structural elements with insubstantial differences from the literal
languages of the claims.
* * * * *
References